Ejector in refrigerating device



Feb. 24, 1970 J. HAISMA 3,496,735

EJECTOR IN REFRIGERATING DEVICE Filed July 5, 1968 2 Sheets-Sheet 1 INVENTOR.

JAN HAISMA Feb. 24,1970 J. HAlsMA 3,496,735

EJECTOR IN REFRIGERATING DEVICE Filed July 5, 1968 2 Sheets-Sheet 2 JAN HASMA INVENTOR.

AGENT 3,496,735 EJECTOR IN REFRIGERATING DEVICE Jan Haisma, Marne, France, assignor, by mesne assignments, to US. Philips Corporation, New York, N.Y., a corporation of Delaware Filed July 5, 1968, Ser. No. 742,624 Claims priority, application Netherlands, July 27, 1967, 6710359 Int. Cl. F25b 1/106 US. Cl. 62-500 3 Claims ABSTRACT OF THE DISCLOSURE An ejector for use in a device for producing cold, the device having a compressed medium cooled and then expanded through the ejector to a first reservoir which communicates through a choke to a second reservoir; by the flow through the ejector the suction side of the ejector draws medium from the second reservoir, the suction pressure being varied by a cone-shaped control pin axially displaceable in the jet tube portion of the ejector nozzle to provide ultra-sonic flow of the medium therethrough.

The invention relates to an ejector particularly suitable for use in a device for producing cold and/or for liquefying gases. Such a device comprises a high-pressure medium supply communicating through one or more heat exchangers in which said medium is cooled to below th inversion temperature associated with said pressure with the jet tube of the ejector; the suction side of the ejector communicates with a minimum pressure reservoir which communicates through a choking cock and, as the case may be, through a further reservoir with the ejector outlet, while with this outlet or with the further reservoir communicates an outlet duct; the jet tube of the ejector includes an axially displaceable control-pin and the jet tube and the control-pin have a conical shape with the same apex at least over the portion lying foremost in the direction of flow.

In connection with the present application an ejector is to be understood to mean a device in which the potential energy of a high-pressure (primary) medium is converted wholly or partly into kinetic energy which is utilized at least partly for raising the pressure of a secondary medium.

These ejectors are particularly suitable for use in cold producing devices of the kind set forth. The advantage is that by drawing off the vapour from the minimum pressure reservoir the cold can be supplied in this reservoir at 'very low temperatures. The medium pressure in the outlet is then considerably higher than that in the minimum pressure reservoir so that, when this medium is caused to exchange heat with the incoming high-pressure medium, the passages for this medium in the heat exchangers concerned, need not be extremely large, while the compression device which again raises the pressure of the medium conducted away is capable of operating with a compression ratio which is considerably lower than the ratio between the pressure of the compressed medium and the vapour pressure in the minimum-pressure reservoir.

-In order to adapt the cold production to the need, it is required to have a possibility of regulating the flow of medium through the ejector. For this purpose it is known to provide in the jet tube of the ejector an axially displaceable control-pin, while the inner wall of the jet tube and the outer wall of the control-pin both have the shape of a cone with the same apex. By the axial displacement of the control-pin the passage of the annular flow channel is varied. Since the inner wall of the jet tube and the wall of the control-pin have the shape of a cone having the same apex, the restriction of the passage, viewed in the United States Patent F 3,496,735 Patented Feb. 24, 1970 direction of flow, will vary with the same ratio in any position of the control-pin. This is important since with any medum flow the variation of the passage is relatively the same so that the effect of the jet tube does not vary with a varying medium flow.

In order to provide cold at very low temperatures the minimum-pressure reservoir has to be drawn off to very low pressures. If, for example, helium is used as a me dium, and it cold has to be produced at 42 K., the pressure has to be reduced to 1 ata.; at a value of 3.6 K. the reduction has to go to 0.5 ata., and a cold production at, for example, 1.75 K. requires a reduction to 0.0015 ata. Inorder to attain these low suction pressures the velocity of the flow out of the end of the jet tube has to be very high. In order to attain high flow velocities it may be necessary to provide an ultrasonic shape of the jet tube, which means that the first portion of the jet tube has to have a passage narrowing in the direction of flow, whereas the second portion (expansion portion) has to have a communicating widening passage.

The invention has for its object to provide an ejector having both a variable passage and an ultrasonic shape, while with any passing flow of the medium the velocity of the medium both in the narrowing portion of the passage and in the widening portion of the passage is invariably at the optimum.

For this purpose the ejector according to the invention is characterized in that over the portion of the jet tube lying downstream viewed in the direction of flow, either the wall of the jet tube or the wall of the control-pin deviates outwardly or inwardly respectively from the conical shape of the first portion so that the annular passage between the jet tube and the control-pin widens in the direction of flow.

Since the widening of the passage of the channel according to the invention is obtained by having either the wall of the jet tube or the wall of the control-pin deviate from the conical surface of the first portion of said elements, the degree of expansion required for an optimum ultrasonic flow of the passage medium does not vary substantially. In this way the ejector can invariably operate at the optimum, so that cold can always be supplied at the same very low temperature, practically independently of the medium flow.

The invention will be described with reference to the drawing.

FIG. 1 shows by Way of example, schematically and not to scale, a device for producing cold at low temperature, in which the expansion is performed in a variable ultrasonic ejector.

FIGS. 2 and 3 show schematically on an enlarged scale two embodiments of the jet tube of the ejector used in the device shown in FIG. 1.

Referring to FIG. 1, reference numeral 1 designates a compressor. The outlet 2 thereof communicates with a supply duct 3 for high-pressure medium. This supply duct includes a plurality of heat exchanges 4, 5 and 6, in which the high-pressure medium exchanges heat with expanded medium, and a plurality of heat exchangers 7, 8, in which the medium is cooled by means of cold-gas refrigerators 9 and 10. Obviously the cold-gas refrigerators may be replaced by other cooling aggregates. After having passed through the various heat exchangers the medium has cooled to a low temperature and is fed to an ejector 11, in which it expands. The expanded medium flows through the duct 12 to the reservoir 13. An outlet duct 14 from the vapour space of the reservoir 13 communicates through the heat exchanges 6, 5 and 4 with the inlet 15 of the compressor 1.

From the reservoir 13 a duct 16 including a choking cock 17 communicates with the minimum-pressure reservoir 18. The vapour space of the reservoir 18 communicates through a duct 19 with the suction side of the ejector 11. In the ejector 11 the potential energy of the high-pressure medium in the jet tube 20 is converted into kinetic energy, which is then utilized for drawing off the vapour from the reservoir 18 and raising the pressure thereof in a ditfusor 21. For obtaining low suction pressures, a high velocity of the outward flow at the end of the jet tube 20 is required. In order to attain these high velocities the jet tube 20 has an ultrasonic shape, which means that over the first portion the passage narrows normally and over the second portion the passage widens in accordance with the local requirements for the ultrasonic flow.

For controlling the cold production the jet tube 20 includes a control-pin 22, which can be inserted into the jet tube over a greater or lesser extent. Two possible embodiments of the jet tube 16 are shown on an enlarged scale in FIGS. 2 and 3. In the embodiment shown in FIG. 2 the control-pin 22 is conical throughout its length. The first portion 23 of the jet tube has the shape of a truncated cone, the apex being equal to that of the control-pin 22. The second portion 24 of the jet tube deviates outwardly from the conical shape so that the annular channel widens over this portion in the direction of flow to an extent such that an ultrasonic flow of the medium is obtained.

Over the portion 23 the passage of the annular channel 25 narrows in accordance with the profile determined by the apex of the cone. When the control-pin is displaced into the position indicated by broken lines, the passage of the channel 25 is reduced, but the narrowing of this channel in the direction of flow varies again in accordance with the same profile.

Over the portion 24 the flow channel widens so that the medium expands. In order to avoid diificulties, at least substantially the same conditions should prevail for any quantity of passing flow, that is to say the same degree of expansion should occur. This is attained by determining the widening of the flow channel by having only one of the boundary walls of the flow channel deviate from the conical shape. In the embodiment shown in FIG. 2 this is the wall of the jet tube. It is thus ensured that with any passing flow the degree of expansion is substantially the same and can be chosen to the optimum.

The same can be achieved by the jet tube shown in FIG. 3, which has the same conical shape throughout its length, while the control-pin has an inwardly deviating shape over the second portion 24. In this way the flow channel is widened by having only the control-pin deviate from the conical shape of the first portion 23. Also in this case the velocity of the outward flow and the suction pressure will be at the optimum with any passing flow.

From the foregoing it will be obvious that the invention provides an ejector which is controllable and has an ultrasonic shape, while the ultrasonic flow profile of the jet tube and hence the suction pressure do not vary with a variation of the position of the control-pin.

What is claimed is:

1. In a device for producing cold which comprises a high-pressure medium source, a supply duct communicating from the source through at least one heat exchanger (in which this medium is cooled below the inversion temperature associated with said pressure) to the jet tube of an ejector, duct means interconnecting the suction side of the ejector with a minimum-pressure reservoir which communicates through a choking cock and a further reservoirwith the outlet of the ejector, and an outlet duct interconnecting said source and the further reservoir, the improvement in combination therewith, comprising an axially displaceable control-pin disposed within the jet tube of the ejector, the jet tube and the control-pin having conical shapes with the same apex at least over the upstream portion of the jet tube, and in the downstream portion of the jet tube, the annular passage between the jet tube and the control pin widening in the direction flow, by deviation from said conical shape of either the wall of the jet tube outwardly or the wall of the controlpin inwardly.

2. A device as defined in claim 1 wherein said jet tube portion of the ejector has a shape for providing ultrasonic flow therethrough.

3. A device as defined in claim 2 wherein the potential energy of the high-pressure medium is converted during said ultrasonic flow in the jet tube into kinetic energy which provides reduced pressure for the suction side of the ejector.

References Cited UNITED STATES PATENTS 1,779,009 10/1930 Negro 103272 2,000,741 5/ 1935 Buckland 103-267 2,000,762 5/1935 Kraft 103267 2,352,094 6/ 1944 Griswold 103-272 3,277,660 10/1966 Kemper 62-500 3,3 60,955 1/ 1968 Witter 62-6 WILLIAM J. WYE, Primary Examiner US. Cl. X.R. 62l91;103-272 

